| 摘要 |
PURPOSE:To simplify the circuit constitution of a receiver for a satellite television, an FM broadcast, and UHF and VHF television broadcasts, by using in common two PLL demodulating circuits for FM and AM demodulators and for extracting AFC and AGC signals. CONSTITUTION:In case of receiving an SHF satellite broadcast which is applied with FM modulation, an input FM signal applied with FM demodulation by a first PLL circuit 4, and also, an AFC voltage is extracted from an output of a loop filter 2, and moreover, an AGC voltage is fetched from an output of a phase comparator 5 of the second PLL circuit 8 which has stopped an operation. In case of demodulating the UHF and VHF television broadcasts which are applied with AM modulation, the input signal is demodulated by the second PLL circuit 8. In such a case, the AFC voltage is extracted from a loop filter 6, and also, the AGC voltage is fetched from an output of a phase comparator 1 whose operation is being stopped. Moreover, in case of an FM broadcast signal, as well, a second PLL circuit 8 is operated and the demodulation is executed, and in the same way as the foregoing, the AFC and AGC voltages are fetched. |
